The technique of separating primary signal sources, which consists of processing mixtures of primary signals to produce an estimate of each primary signal, is known. Said technique is applied to primary signals resulting from independent sources, which signals are only available in the form of said mixtures. This may relate to convolutional linear mixtures or instantaneous linear mixtures. They may be generated by propagation mechanisms of primary signals and/or by superposition mechanisms for signals that result from various sources or other causes.
Generally, the technique of source separation works "in the blind", that is to say, the sources are supposed to be unknown, to be independent, to have unknown mixtures. Therefore, various samples of said mixtures are detected on the basis of which the use of separation algorithms permits of restoring one or various estimates of the original primary signals.
Such a technique, applied to the separation of instantaneous linear signal mixtures is disclosed, for example, in the document entitled "Separation of Independent Sources from Correlated Inputs" by J. L. Lacoume and P. Ruiz, IEEE Transactions on Signal Processing, Vol. 40, No. 12 Dec. 1992, pages 3074 to 3078.
For effecting the source separation, that is to say, obtaining on the output an estimate of each source that forms the mixture, this document reveals a method of calculating cumulants, For this purpose, it teaches to adapt parameters of the source separation system in such a way that cumulants of output signals which are expressed as a function of cumulants measured on the input signals resulting from the mixtures are set to zero, while the cumulants are of a higher order than the second order. By setting these cumulants to zero, inverse mixing coefficients are indirectly derived to obtain an inverse transform of the transform obtained from the application of mixing operations to the primary signals. The teaching of this document leads to giving a direct structure to the system of source separation. Moreover, as the input signals are statistically dependent because they result from mixtures, the equations that link the cumulants of the output signals to the cumulants of the input signals are very complex.
Such a technique has turned out to be very complex to implement and does not yield a simple solution in the case of real signals which generally result from instantaneous linear mixtures.